1. Field of the Invention
The invention generally relates to methods for forming frozen hollow spheres and more particularly to an improved method of utilizing a drop tower for forming hollow glass spheres in the absence of shape-distorting effects of aerodynamic drag.
2. Description of the Prior Art
Since thermo-nuclear fusion is an extremely important segment of scientific endeavor, laboratory experiments are continuously being conducted in this field. One area of fusion research, known as inertia-confinement, has received much attention from those experimentors currently employed in this endeavor. In this area, electronic means are finding a prominent place among the drivers being proposed.
Briefly, inertial-confinement is attained by radiating a target with extremely high intensity beams such as, for example, laser, ion, and electron beams. Such a beam of radiation is applied over a very short time span, such as 100 pico seconds, for example. The targets employed preferably comprise hollow spherical shells of glass filled with deuterium and tritium. Conversion of the target surface to plasma occurs in about 10 pico seconds, causing inward compression of thermo-nuclear fuel contained in the spheres. The mass of fuel is burned at its center as a result of the implosion where the compression is high enough. Compression to more than 1,000 times liquid density is desired for reasonable reactor-target design. Currently, reactors tend to need approximately 50% fuel burned in order to be considered efficient. Spherical glass shells are considered, currently, to comprise the best primary fuel containers for targets, in a laser fusion process, because of their high strength and low permeability.
Presently, the spheres employed as research targets are characterized by an outside diameter of approximately 100 micrometers and a shell thickness of approximately 1 micrometer. However, reactor target sizes ranging from one to ten millimeters in diameter have been considered. Glass shells with aspect ratios, that is to say, having outside diameters to wall thickness as high as 500-1 have been produced. However, as is well known, as the aspect ratio increases, the yield of high-quality shells tends to diminish. Therefore, one of the major problems facing those currently involved in research of the type aforementioned, is how to obtain a sufficiently high yield of spheres having the precise sphericity and concentricity needed to facilitate a desired enhanced efficiency.
During the course of a preliminary search conducted for the instant invention, the patents discovered are listed on the enclosed "List Of Prior Art Cited By Applicant".
The patent to Kassel U.S Pat. No. 2,738,548 discloses a pellet-forming apparatus in which globs of molten material are dropped into a flow of liquid flowing in the same direction as the molten material. The patentee there was concerned with a method of manufacturing pellets in which is included the step of dropping successive pellet-globules from an orifice downwardly through a closely confining tubular film of cooling fluid for thus cooling the globule. It is noted that the molten globules fall successively through a ring-like or tubular fluid film such that the globules are cooled relatively rapidly by the fluid comprising the film. The fluid film is vaporized to provide steam or vapor directly below the leading edge or bottom portion of the globules. The steam or vapor, in turn, tends to provide a slowing of the rate of fall or descent for each of the globules whereby the globules and resulting pellets are maintained within the length of tubular film for a longer period of time than they would be if they were to fall entirely freely without encountering the cushioning effect resulting from the rising counter current flow of steam. Additionally, there is provided a steam collecting zone for providing upward flow of steam through the tube, with respect to the molten globules and pellets. Such necessarily results in out-of-round pellets. It is therefore believed that the patentee Kassel fails to disclose or suggest the invention hereinafter more fully described and claimed.
The patent to Laehder U.S. Pat. No. 3,059,280 is believed to be of interest in that this patent discloses a system for forming urea prills wherein a downwardly moving stream of air is used to cool and solidify the prills in a prilling tower, however, it also is clear that the patentee Laehder fails to suggest the use of a drop tower wherein a stream of downwardly flowing air is accelerated at precisely one-G in order to overcome the effects of otherwise encountered aerodynamic drag.
The remaining patents to Robinson, Haas et al, Faulkner and Landis also are believed to be of interest. However it is believed that these patents fail to suggest applicant's invention as hereinafter more fully described and claimed.
For example, the patent to Robinson discloses in a glass bead-making furnace converging structure for an air-stream flowing in a direction of a smaller area; the patent to Haas et al discloses a method wherein gel microspheres are prepared by passing a stream of material into an organic drying liquid stream at an angle to its direction of flow to effect a high shearing force in droplet formation; the patent to Landis discloses a formation of urea droplets using a downwardly flowing gas stream in a prill tower, and then cooling the collected prills thus formed in a fluidized bed having a second gas stream flowing in a counter current direction relative to the prill; and the patentee Faulkner discloses a method and apparatus for making fibers.
It is therefore, the general purpose of the instant invention to provide a method for forming uniformly shaped glass spheres characterized by precise sphericity and concentricity in a terrestrial, substantially zero-G environment.